Non-curling decalcomania paper comprising a discontinuous polymer-starch particlebarrier layer

ABSTRACT

A WATER RELEASABLE DECALCOMANIA PAPER INCLUDES A BASE MEMBER SUPPORTING SEVERAL LAYERS, E.G., A NON-POROUS BARRIER LAYER, A NON-BLOCKING ADHESIVE FILM TOP COATING AND THE DECALCOMANIA PRINTING OR LACQUER. THE NON-POROUS BARRIER LAYER, CONTAINING INDIVIDUAL PARTICLES OF STARCH AND A DISCONTINUOUS POLYMER PHASE PREVENTING CONTACT BETWEEN AT LEAST SOME OF THE STARCH PARTICLES, PREVENTS PASSAGE OF WATER INTO THE BASE DURING APPLICATION OF THE TOP COATING, THE LATTER FORMING THE ADHESIVE FOR THE DECALCOMANIA PRINTING AND MADE UP PRIMARILY OF DEXTRIN. A POLYVINYL ALCOHOL OR METHYL CELLULOSE LAYER MAY BE DEPOSITED ON THE DEXTRIN, THE DEXTRIN BEING MECHANICALLY OR CHEMICALLY BROKEN. THE DECALCOMANIA PAPER MAY BE OF THE SIMPLEX OR DUPLEX TYPE AND MAY BE OF THE &#34;FACE-DOWN&#34; OR &#34;SLIDE-OFF&#34; VARIETY.

June 13, 1972 -r. L. REILING 6 ,7 4

NON-CURLING DECALCOMANIA PAPER COMPRISING A DISCONTINUOUS POLYMER-STARCH PARTICLE BARRIER LAYER Filed Nov. 28. 1969 FIG-1 A PR'NTING -I;\\\\\\\\\ ADHESIVE 2 BARRIER LAYER INTING ADHESIVE TISSUE BARRIER LAYER PAPER FIG-3 PRINTING POLYVINYL ALCOHOL ADHESIVE BARRIER LAYER PAPER l/V VE/V TOR THOMAS L. REILING ww w A TTOR/VEYS United States Patent NON-CURLING DECALCOMANIA PAPER COM- PRISING A DISCONTINUOUS POLYMER- STARCH PARTICLE BARRIER LAYER Thomas L. Reiling, 200 Walnut St, Dedham, Mass. 02026 Filed Nov. 28, 1969, Ser. No. 880,722 Int. Cl. B4lm 3/12 US. Cl. 1173.6 11 Claims ABSTRACT OF THE DISCLOSURE A Water releasable decalcomania paper includes a base member supporting several layers, e.g., a non-porous barrier layer, a non-blocking adhesive film top coating and the decalcomania printing or lacquer. The non-porous barrier layer, containing individual particles of starch and a discontinuous polymer phase preventing contact between at least some of the starch particles, prevents passage of water into the base during application of the top coating, the latter forming the adhesive for the decalcomania printing and made up primarily of dextrin. A polyvinyl alcohol or methyl cellulose layer may be deposited on the dextrin, the dextrin being mechanically or chemically broken. The decalcomania paper may be of the simplex or duplex type and may be of the face-down or slide-off variety.

BACKGROUND OF THE INVENTION This invention relates to decalcomania paper and more particularly to an improved decalcomania paper of the simplex or duplex type.

Decalcomania paper usually includes a backing sheet having thereon a coating which is dry and non-tacky under normal conditions and capable of receiving a lacquer coating or decalcomania printing. When activated by water the transfer or separable layer should be easily releasable regardless of whether it be a slideolf or facedown decalcomania.

One of the difliculties heretofore present with decalcomania paper is the tendency, in the unactivated state, to curl for reasons well known in the art. Such curl is a problem because of the difliculty associated with printing, the latter usually done by a silk screening method. Breaking the sheet after the application of the adhesive for the transfer creates problems because the lacquer used in the decalcomania printing penetrates the broken glue layer and firmly anchors the transfer to the remainder of the sheet thus rendering it difficult to slide the transfer off after activation.

It has also been the procedure in the prior art to calendar the sheet following the application of the various coatings in order to provide smooth layers. This calendaring procedure, however, builds up strains in the sheet.

US. Pat. No. 2,733,997 of Feb. 7, 1956, describes a decalcomania paper in which a water-leaf paper is coated with a sizing made up of clay in a hinder, the latter being overcoated with an adhesive, which in turn is covered by a top gumming usually dextrin, the dextrin either being lacquer coated, or having printing applied to the top gumming. During activation, the slide-off separation occurs in the bottom gumming layer so that the adhesive surface of the transfer is in large measure made up of the bottom gumming and a portion of the size coating.

Where decalcomania papers include clay size coating, the resultant sheet includes considerable ash residue which is objectionable for many uses. For example, in the manufacture of chinaware, the decorative patterns and images are applied by decalcomania and thereafter fired to form the pattern permanently on the chinaware. Where the dual transfer includes clay particles, the fired image is hazy in appearance because the clay is fired over the pattern. To overcome this difiiculty the practice is to use a duplex decalcomania as a slide off, thus requiring considerable soaking of the decalcomania to effect release at the tissue interface. Because the tissue has low ash content, the problem of haze is eliminated, but the process of transfer separation is somewhat involved.

One of the sources of the curl is the penetration of water from the coating mixture into the base sheet, if the coatings are applied from an aqueous system. For example, the size coating of the Asnes patent is applied from an aqueous mixture which includes a substantial amount of water. The remaining layers are also applied from aqueous systems including a considerable amount of water. Due to the amount of water used, it penetrates the interface between the size layer and the paper base causing curl. This problem is solved in Asnes by wetting the exposed surface of the paper with water and drying the sheet under tension after each coating operation.

SUMMARY OF THE INVENTION In accordance with the present invention, the above difiiculties are overcome by the use of a barrier coating deposited from a predominantely solvent system, the barrier coating operating to prevent penetration of water into the paper during the subsequent coating operations. Also, the product of the present invention eliminates the need of the size coatings heretofore used in decalcomania paper, resulting in a product which has very low ash content and which is flat before activation. The barrier coating is non-porous and quite smooth, and thus it is not necessary to calendar the coated sheet after each coating operation. Thus, in accordance with this invention, calendaring is not necessary and the sheet retains its original flatness.

Accordingly, it is a primary object of the present invention to provide an improved non-curling decalcomania paper.

Another object of the present invention is the provision of a decalcomania paper of the type described utilizing a barrier layer which prevents water from penetrating into the base sheet during coating, but which on activation permits passage of water from the base sheet into the barrier layer enabling release of the transfer.

Another object of the present invention is the provision of a non-curling decalcomania paper having low ash content.

DETAILED DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view of the improved decalcomania paper of the present invention;

FIG. 2 is a cross-sectional view of an improved duplex decalcomania paper of the present invention; and

FIG. 3 is a view in section of a modified form of decalcomania paper in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, (which are for purposes of illustration and are not drawn to scale), a preferred form of the invention is shown in FIG. 1 in which a paper base 1 has on its surface several layers including a smooth, non-porous barrier layer 2 and an adhesive layer 3. In the form shown, the decalcomania paper is of the simplex type, the outer surface of the adhesive 3 including printing, or a lacquer film which is applied to the adhesive layer.

In the form shown in FIG. 2, which illustrates a duplex system and wherein the same reference numerals "ice have been applied where applicable, a sheet of tissue isinterposed between the adhesive layer. and the barrier layer.

The paper base which is Water-leaf is customarily used in decalcomania papers because of the high rate of water absorption and penetration of the uncoated side. Other successful base stocks may be used as is well known to those in the art.

Applied over the base stock is the barrier coating which includes starch particles adhered to each other and to the base by their natural adhesive properties and forming a first discontinuous phase. Also present in the barrier coating is a discontinuous phase of polymer which prevents contact between at least some of the starch particles, the two discontinuous phases cooperating to form a non-porous film which, after its deposition and drying, prevents water used in the application of the successive coatings from penetrating into the interface between the barrier layer and the base material. For further details relating to the barrier layer, reference is made to U.'S. Pat. 3,425,968, issued Feb. 4, 1969.

A typical composition of the barrier coating includes between to 35% polymer based on the total solids of the coating, the balance being starch, or starch and a small amount of plasticizer such as glycerine. A typical coating composition for forming the barrier coating, is as follows:

Grams Water 43 Methanol 50 Glycerine 25 Toluene 210 Starch 180 Polymer 23 1 Solids basis.

The polymers which may be used are copolymers of ethylacrylate and methylmethacrylate, such as RHoplex B-lS, or RHoplex B-19 (believed to be a methacrylate polymer dispersed in water), a methacrylate-vinyl acetate copolymer dispersed in water (RHoplex WG-6) or RHoplex B-lO, believed to be a carboxylated ethylacrylate copolymer of lower molecular weight than the B-15. Other materials which may be used are copolymers of butadiene and styrene and homopolymers of polyvinyl acetate in emulsion form. The procedures for forming the coating mixture are described in US. Pat. 3,425,968, previously referred to.

After application and drying of the barrier coating, the exposed surface is relatively smooth and it is not necessary to calender the barrier coating. Also, it will be noted that the predominant liquid component of the barrier coating mixture is an organic solvent thus eliminating the problems associated with absorption or penetration of water by the base stock during application of the barrier coating. In the range of 15 to 30% by weight of polymer based on the solids content of the barrier coating, the release of the transfer is fairly rapid. If, however, slower release is required, the percentage by weight of polymer based on barrier layer solids should be increased, but not appreciably more than 35 Following application of the barrier layer, either the tissue layer is applied to provide a duplex sheet as ilustrated in FIG. 2, or the adhesive layer is applied. The preferred adhesive for layer 3 is dextrin applied from a water solvent mixture, a small amount of solvent being used to prevent penetration of water into the barrier layer, or the tissue layer in the case of duplex decalcomania.

A typical dextrin coating mixture is as follows:

Pounds Pelargonic acid 1.6 Glucose 23.4 Water 140 Isopropyl alcohol 39 The resulting mixture has a viscosity of 200 cps at F. The isopropyl alcohol prevents substantial penetration of the water into the undercoatings and enhances the action of the acid which is used to efiect chemical breaking of the dextrin film. Other fatty acids which may be used include azelic, stearic or any of the nine carbon monobasic or dibasic acids. The range of the acid for chemical breaking of the dextrin is between 1% and less than 25 based on the weight of dextrin Above' about 25% the film is broken sufficientily to permit the lacquer to penetrate and to anchor into the dextrin layer. In most cases, 10% of the acid based on the weight of the dextrin operates satisfactorily and microscopic examination of the film establishes that the film is broken, although not broken mechanically. In addition to acids and fatty acids, materials such as margarine may also be used, as well as polyethylene glycol and methoxypolyethylene glycols although the latter provide a dull film which may be objectionable for face-down decalcomania which requires gloss.

It is also possible in accordance with the present invention to utilize a mixture of dextrin and polyvinyl alcohol, as the adhesive medium for the transfer. A typical such coating formulation is as follows:

Grams Polyvinyl alcohol (Gelvatol 40-20) 80 Dextrin 300 Water 500 The above ingredients are mixed in a Barrington mixer at 212 for approximately 20 minutes and thereafter cooling to T o the above cooled mixture, 200 grams of isopropyl alcohol and 100 grams of toluene are added and the mixture is cooled'to room temperature and may be applied either to the tissue sheet or the barrier coating.

It is also possible to use separate layers of dextrin and polyvinyl alcohol to produce a sheet illustrated in FIG. 3 in which a polyvinyl alcohol layer 6 is deposited over the dextrin layer 3. A typical formulation for using polyvinyl alcohol as a separate layer is as follows:

Pounds Polyvinyl alcohol (Gelvatol 40-20) 100 Water 80 Methanol 200 used, it operates to hold out the lacquer image and provide adhesion when the film is released by water activation.

In the place of the polyvinyl alcohol layer previously described, a layer of dextrin, polyvinyl alcohol and a copolymer of ethylacrylate and methyl methacrylate (RHoplex B-15 or RHoplex B-lO, previously described. A typical formulation includes Grams Dextrin 75 Polyvinyl alcohol 25 Ethylacrylate copolymer, supra 5 1 Wet basis-appr0ximately 40% solids.

The alcohol is dissolved in 100 grams of water and the dextrin is added and the mixture cooked at 180 F. until the dextrin is dissolved. Thereafter the acrylate copolymer is added followed by 100 grams of equal amounts of toluene and methanol. When applied, the coating mixture provides a glossy film which also acts as an adhesive for the transfer.

Upon activation of the sheet, Water penetrates through the base stock into the barrier coating to activate the starch therein, and to activate the dextrin layer, the activated starch operating to hold the water to permit the transfer, which includes the printing, the adhesive layer and a small amount of the barrier layer, to be slipped off. Since the barrier layer does not include pigmented materials, the ash content of the transfer is extremely low thus enabling it to be used. In those instances in which residual ash presents problems, for example, in decalcomania for chinaware or other refractories in printing is applied and thereafter fired.

The decalcomania in accordance with the present invention is much flatter than the decalcomania of the prior art, has improved dimensional stability and better printability because of the lay-flat character. Since the amount of water used in the coating procedure is controlled, particularly in the case of the barrier layer, it is not necessary to treat the coated base under tension between each coating operation. Moreover, the dextrin material may be broken chemically, or if desired broken mechanically in which event the polyvinyl alcohol layer is utilized to prevent the printing on the lacquer from penetrating into the mechanically broken dextrin layer.

The particular barrier layer described in accordance with the present invention in addition to offering the advantages already noted, also provides a very smooth surface which eliminates the need for calendaring or flattening the surface of the coating by some mechanical operation before deposition of the dextrin in the simplex type decalcomania.

While the products and the process herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise products and process, and that changes may be made therein without departing from the scope of the invention.

What is claimed is:

1. A decalcomania paper for carrying decalcomania printing comprising a cellulosic base member supporting a plurality of coatings including a smooth, non-porous barrier coating over said base member which prevents passage of Water into said base member during coating, a flexible, non-blocking water soluble continuous film top coating over said barrier coating which is resistant to decalcomania ink solvents and which forms the adhesive for said decalcomania printing, said barrier coating including a discontinuous phase of individual particles of starch adhered to each other and to the cellulosic base upon which they are deposited by the natural adhesive properties of the starch and a discontinuous phase of polymer preventing contact between at least some of said starch particles, and said barrier coating operating during activation of the decalcomania to permit passage of water to said adhesive for activation thereof thus permitting release of the decalcomania printing and at least said adhesive top coating.

2. A decalcomania paper as set forth in claim 1 wherein said adhesive for said decalcomania printing comprises a layer of dextrin deposited on said barrier coating and a hold out layer composed of a non-blocking water dispersible, solvent resistant gum capable of forming a flexible film.

3. A decalcomania paper as set forth in claim 2 wherein said dextrin layer is broken and said hold out layer seals said broken dextrin layer to prevent adhesion of the decalcomania printing to said barrier coating.

4. A decalcomania paper as set forth in claim 1 wherein said top coating is broken.

5. A decalcomania paper as set forth in claim 3 wherein said dextrin layer is chemically broken.

6. A decalcomania paper as set forth in claim 1 Wherein said barrier coating contains between 10% and 35% by weight of a water insoluble polymer which forms said discontinuous phase.

7. A decalcomania paper as set forth in claim 1 wherein said barrier coating is uncalendared, and wherein the adhesive coating is applied directly to said barrier coating and consists of superimposed layers of dextrin and a hold out layer composed of a non-blocking water dispersible, solvent resistant gum capable of forming a flexbile film.

8. A decalcomania paper as set forth in claim 7 wherein said hold out layer has deposited thereon decalcomania printing which along with said adhesive coating is releasable by activation of water, said barrier coating being operative upon activation to transfer water from said base member to said adhesive coating.

9. A decalcomania paper as set forth in claim 7 wherein said adhesive layer is broken.

10. A decalcomania paper as set forth in claim 6 wherein said barrier coating includes glycerine present in an amount not greater than 25% by Weight.

11. A decalcomania paper as set forth in claim 1 wherein said starch is present in an amount by weight of at least three times the weight of the polymer.

References Cited UNITED STATES PATENTS 2,047,700 7/1936 MacLaurin c 161266 2,184,077 12/1939 Hart 117-3.6 2,561,976 7/1951 Davis 1173.6 2,578,150 12/1951 Rathke 117-36 2,629,670 2/ 1953 Rathke 1173.6 2,733,997 2/ 1956 Asnes 1l73.5 3,007,829 11/1961 Akkeron 161-413 3,425,968 2/1969 Reiling 1 17--122 X ROBERT F. BURNETT, Primary Examiner D. I. FRITSCH, Assistant Examiner US. Cl. X.R. 

